Metastasis of primary tumors to distant organ sites is mainly responsible for high cancer fatality. This migration progress is believed to be assisted by a family of hydrolytic enzymes including matrix metalloproteinases (MMPs). MMPs define the cellular environment through selectively degrading both extracelluar matrix and non-matrix proteins, and are low or undetectable in most normal tissues, but substantially increased in the majority of malignant tumors. The extent of their expression has been shown to be related to tumor stage, invasiveness, metastasis and angiogenesis. The recent disappointing results of clinical trails of MMP inhibitors, however, emphasize the need for better understanding of the mechanism by which this family of multifunctional proteases contributes to multiple steps of tumor growth and progression, from initiation, angiogenesis, and the establishment and growth of metastatic lesion in distant organ sites. This research proposes to develop a novel nanotechnology-based sensing and imaging system for sensitive, accurate, and multiplex detection and imaging of MMPs in biological samples and in living subjects and apply this new technique to investigate the functional roles of MMPs in the tumor formation, growth and progression. This new platform is based on quantum dots (QDs) and bioluminescence resonance energy transfer (BRET). Quantum dots are tiny fluorescent semiconductor nanocrystals that can be produced with a spectrum of defined emission wavelengths and used for multiplex detection. QDs can emit light via the resonance energy transfer process from a light-emitting protein in the process of QD-BRET. This research will develop a series of nanosensors based this QD-BRET platform to detect and image three important proteases that highly involve in tumor metastasis: MMP-2, gelatinase A responsible for the degradation of type IV collagen, the main component of extracellular matrix; MMP-7, matrilysin, the smallest member with broad proteolytic activity; and urokinase-type plasminogen activator (uPA) that involves the activation of MMPs. There are three specific aims: 1) to establish the QD-RBET detection platform for multiplexing analysis of MMP-2, MMP-7, and uPA in biological samples (in cell medium and mouse serum); 2) to multiplex image MMP-2, MMP-7, and uPA activity in xenografted tumors in a mouse model; 3) to image the inhibition efficacy of uPA, MMP-2 and MMP-7 by small interfering RNA and to probe the cross-activation relationship among the three proteases. This QD- BRET sensing and imaging nanoplatform will be invaluable for both early detection of biomakers and for in vivo real-time monitoring of tumor activity and function. The strategy developed here can also be extended to many other targets as well. A sophisticated understanding of the differences in proteolytic activity between tumor and normal tissues in living subjects will advance our understanding of cancer metastasis and help develop anti- metastasis therapy. PUBLIC HEALTH RELEVANCE: The proposed research aims to develop novel nanotechnology to detect and image critical enzymes that facilitate tumor migration from primary sites to remote organs. This new nanotechnology will allow highly sensitive detection of these enzyme molecules in biological samples to help early detection of cancers. A sophisticated understanding of the differences of enzyme activity between tumor and normal tissues in living subjects will advance our understanding of cancer metastasis and help develop antimetastasis therapy.